Ganglioside‐mediated Metabolic Synchronization of Protein Synthesis Activity in Cultured Hepatocytes

Abstract

An ultradian oscillation of protein synthesis was detected by synchronization of metabolic activity in rat hepatocyte cultures. This oscillation occurs in dense cultures in fresh medium, but not in sparse ones. Metabolic synchronization of sparse cultures, however, was initiated by conditioned medium or addition of 0.3-0.5 microm of a mixture of bovine brain gangliosides to fresh culture medium along with either 0.06-0.2 microm GM1 or 0.1-0.2 microm GDIa. GTIb and GDIb did not produce oscillations, nor did human liver ganglioside GM3. High expression of GM1 ganglioside determinants in hepatocytes maintained in the conditioned medium purified polyclonal antibodies to GM1 was coupled with protein synthetic oscillatory activity, i.e. metabolic synchronization. Incubation of dense cultures with GM1-antibodies for 24 h decreased the amplitude of these oscillations. In sparse cultures maintained in fresh medium where protein synthesis showed no oscillatory pattern, GM1 expression was low.

Shedding and uptake of gangliosides and glycosylphosphatidylinositol-anchored proteins

“…In addition to its role in the modulation of lipid rafts, shedding and uptake of gangliosides and GPI-linked proteins might be involved in some other processes. For example it was hypothesized that shed gangliosides might be involved in cell synchronization [270,271]. The fact that shed ganglioside suppress immune response to cancer cells suggest that this mechanism could actually be used to suppress autoimmune response in some situations.…”

Age-related features of protein synthesis rhythm. Effects of extracellular medium

“…Experiments were carried out on cultures of hepatocytes obtained from the liver of rats: 14 old (age 2-2.5 years, weight 610-680 g) and 30 young (3-3.5 months, 250-270 g). The method of isolation and cultivation of hepatocytes was already described in detail (Brodsky et al , , 2000b. The liver was perfused by a calcium-free Hanks solution with 0.5 mM EDTA and 0.05% collagenase (Sigma, USA) in medium 1999.…”

“…4% of others) or individual fractions (GM1 or GD1a). The synchronizing effect of gangliosides can be reproduced by a medium conditioned by dense cultures (Brodsky et al , 1995(Brodsky et al , , 2000b.In order to simulate the influence of gangliosides on intracellular processes, we studied their well known effect on the concentration of calcium ions in the cytoAbstract -Cell interactions have been studied in cultures pf hepatocytes from young and old rats. The rhythm of protein synthesis is an index of cell interaction and synchronization in culture, while the amplitude of oscillations characterized cell cooperation in an aggregate rhythm.…”

“…4% of others) or individual fractions (GM1 or GD1a). The synchronizing effect of gangliosides can be reproduced by a medium conditioned by dense cultures (Brodsky et al , 1995(Brodsky et al , , 2000b.…”

Immune Response Modulation by Tumor-Secreted Glycosphingolipids

“…The physiologic significance of GSL shedding and uptake is unknown. By transferring molecules, GSL shedding provides a mechanism to alter diverse surface properties on donor and/or acceptor cells [75][76][77][78][79]. In tumors, GSL shedding occurs rapidly (≈0.1 to 0.5% of total cell GSL per hour [59,67]).…”